Conventionally, an offshore drilling platform is fabricated in a harbor or an on shore location and then towed to a marine site where it is tipped on end and lowered so that the legs of the platform rest on the ocean floor. Traditionally, these legs are hollow structures so that pillings can be driven downwardly through the legs and into subterranean formations below the ocean floor. In the installation of such systems, it is desirable to fill an annulus between the piling and the platform legs as may exist so that the system is a rigid unitary structure when completely installed. Further, it is desirable that the grout that is to be placed in such annulus be maintained free from contamination and debris as might be otherwise present if measures were not taken to prevent the influx of such materials in the course of installation of the system. Heretofore, grout seals have proven to be unreliable in sealing the annulus between the piling and platform legs.